<p><b><i>Background:</i></b> Though methotrexate (MTX) is known to
inhibit proliferation of trophoblasts derived from ectopic and
intrauterine pregnancies, its action on trophoblasts derived from
postpartum placenta remains questionable. This study was designed to
ascertain the efficacy of MTX in inducing cell death of postpartum
placental cytotrophoblasts (PPTC). <b><i>Methodology:</i></b> Primary
human cytotrophoblasts were isolated from placentae of 1st and 2nd
trimester intrauterine pregnancies and from postpartum placentae. The
isolated trophoblasts were identified based on the expression of
cytokeratin 7. MTX-induced inhibition of proliferation of
cytotrophoblasts was detected by flow cytometry combined with the WST-1
assay. Secretion of HCG-β and invasiveness were evaluated to assess the
effect of MTX on blocking the differentiated cellular function of
cytotrophoblasts in relation to the gestational age. The efficacy of MTX
in inducing apoptosis of cytotrophoblasts was estimated by terminal
deoxynucleotidyl transferase-mediated dUTP nick end labeling. <b><i>Results:</i></b>
MTX significantly inhibited the proliferation and differentiation of
cytotrophoblasts. MTX-induced cell apoptosis of PPTC was confirmed by
increased expression of Fas, FasL, Bax, cleaved caspases 3, 7, 8, and 9,
and decreased expression of Bcl-2. <b><i>Conclusion:</i></b> MTX inhibits replication and differentiation of cytotrophoblasts and appears to be an efficient inducer of PPTC apoptosis.</p>